Pros
For someone who is professionally mature and doesn't obsess about what benefits their friend of a friend is getting at Google, R/GA offers great opportunity for an Experience Designer. Turnover breeds opportunity for you to pounce on. Like anywhere else, when you take ownership of your tasks, you'll be entrusted to do more. Great benefits package, decent pay, 18 days paid-time-off, corporate discounts depending on the accounts you work on.
Cons
Office camaraderie exists within your working and desk groups. It doesn't naturally happen even though you travel in the same space. I think it's easy to get lost in the mix, self-motivated diligence to making yourself visible is key to your success and your satisfaction. Work-life balance is dependant on the team. For me, it has been a wonderful balance. There are long days occasionally, but most of the time, as long as you work well, you don't have to stay late.